Synthetic fluoride containing zeolite systems

ABSTRACT

1. A METHOD OF PRODUCING FLUORINE CONTAINING ZEOLITE MOLECULAR SIEVES COMPRISING: (A) PROVIDING A REACTION MIXTURE OF AN ACTIVE ALUMINA SOLUTION AND AN ACTIVE SILICA SOLUTION WHEREIN THE RATIO OF ALUMINA TO SILICA IN SAID SOLUTIONS IS EFFECTIVE TO PRODUCE A ZEOLITIC COMPOSITIONS; (B) PROVIDING A FLUORIDE ION SOLUTION WHEREIN SAID FLUORIDE ION SOLUTION WHEREBY A SLURRY FORMS; THE COMPOUND SELECTED FROM THE GROUP CONSISTING OF AMMONIUM FLUORIDE, AMMONIUM FLUOSILICATE, HYDROGEN FLUORIDE AND FLUOSILICIC ACID, SAID ANION RADICAL BEING PRESENT IN A RATIO OF FROM 0.5 TO 50 PERCENT OF THE ACTIVE ALUMINA CONTENT OF SAID REACTION MIXTURE; (C) ADMIXING SAID ACTIVE ALUMINA, ACTIVE SILICA AND FLUORIDE ION SOLUTIONS WHEREBY A SLURRY FORMS; (D) AGING SAID SLURRY AT A TEMPERATURE OF FROM ABOUT 20*C. TO 120*C. FOR FROM 1 TO 48 HOURS, WHEREBY A CRYSTALLINE ZEOLITE IS FORMED WHICH HAS FROM ABOUT 0.01 TO 0.15 PERCENT FLUORIDE COORDINATED INTO THE CRYSTALLINE STRUCTURE; AND (E) RECOVERING SAID CRYSTALLINE ZEOLITE.

United States Patent Qfice- 3,839,539 SYNTHETIC FLUORIDE CONTAININGZEOLITE SYSTEMS Curtis Homer Elliott, Jr., Baltimore, Md., assignor toW. R. Grace 8: Co., New York, N.Y.

No Drawing. Continuation-impart of application Ser. No. 803,117, Feb.27, 1969, now Patent No. 3,594,331. This application Oct. 4, 1971, Ser.No. 186,458 The portion of the term of the patent subsequent to July 20,1988, has been disclaimed Int. Cl. Blllj 11/40, 1 1 78; C01b 33/28 US.Cl. 423329 15 Claims ABSTRACT OF THE DISCLOSURE Fluoride containingzeolites are produced from an admixture of active silica source andactive alumina source solutions by incorporating a fluoride compound offluosilicate compound in this initial zeolite precursor react-antsolution. As the zeolite is formed, the fluoride is incorporated intothe zeolite at a concentration of about 0.01 to 0.15 percent by weight(dry basis). The result-ing zeolites have higher thermal and steamstabilities, higher surface areas, smaller crystallites and lowercontaminant content. The presence of the fluoride in the precursorsolution enhances these properties of the zeolite.

This application is a continuation-in-part of my application Ser. No.803,117, filed Feb. 27, 1969, now US. Pat. 3,594,331, issued July 20,1971.

In my first application, now US. Pat. 3,594,331, concerning theincorporation of fluoride ions into a zeolitic molecular sieve, thefluoride ions were incorporated into the sieve after the zeolite hadbeen fully synthesized, 01' for that matter into naturally availablezeolites by a contacting technique. This contacting technique providesthe sieve with an unwashable fluoride content of .01 to .15 percent.This fluoride content yields a zeolite having a substantially greaterhigh temperature thermal and steam stability.

Since the filling of my initial application sever-a1 others in the arthave developed varying techniques for incorporating fluoride into thestructure of the molecular sieve. However, these techniques developedthus far consist of varying post treatments of the zeolite in order toincorporate the desired fluoride content into the zeolite. Exemplary onthis point is 3,575,887 which discloses the treating of a zeolite with afluoride and chloride containing solution. This method, although it doesincorporate fluoride into the zeolite structure, requires the addedtreating step. My present invention is a distinct improvement over thisand the techniques of my earlier application by allowing the fluoride tobe incorporated into a synthetic zeolite during the synthesis of thezeolite. And besides the savings in decreasing the number of steps,there are other advantages. One advantage is that large quantities ofdilute fluoride solutions are not required, lessening the disposalproblems in view of the ever more stringent pollution controls. Otheradvantages are that the zeolites produced have higher surface areas andsmaller crystallite size. Another advantage is that a purer zeolite isformed. In some way, the fluoride suppresses contaminant formationduring crystallization.

It is, therefore, a prime object of this invention to set out atechnique whereby fluoride ion can be incorporated into a zeolitestructure during the synthesis of the zeolite.

-It is further an object of this invention to produce fluoridecontaining zeolites wherein the fluoride is present in the zeolitestructure in an unwashable condition.

It is additionally and particularly an object of this invention toproduce fluoride containing zeolites which have Patented Oct. 1, 1974 :agreater thermal and steam stability and which can therefore be veryeffectively used as active components in petroleum cracking orhydrocr-acking catalysts.

In brief summary, the present invention consists essentially ofproviding a fluoride ion source along with a reactive silica source anda reactive alumina source, and reacting this mixture to form a reactionproduct containing incorporated fluoride ion. This reaction product isthen aged and crystallized to form the particular crystalline zeolite.The fluoride in this zeolite is held in the crystalline structure in atightly bound unwashable condition. The zeolite after crystallizationcan then be dried and activated, or may undergo an exchange of thesodium ions with potassium, ammonium, alkaline earth, transition metalor rare earth metal ions. In essence, any of the known stabilizingprocedures may be performed on the fluoride containing crystallinezeolite in order to further enhance the stability or other properties.

In more detail, my invention consists in producing synthetic crystallinezeolites having fluoride coordinated into the structure. The syntheticzeolites which can be produced containing this coordinated fluorideinclude the zeolites which in the hydrated form are designated by theformula where M is a cation, n represents the valence of the cation, Wthe moles of silica. The commercially important synthetic zeolitesdesignated A, X and Y by Linde Division of Union Carbide are in one modedifferentiated from each other in the Si0 content (W value).Conventionally a Zeolite A has a W value in the range of 1.85, Zeolite Xin the range of 2-3 and Zeolite Y in the range of greater than 3 to 7.Of course there are other differences such as in pore size, crystallinestructure, adsorption capacities and so on, but the variation in silicacontent provides a very convenient means of description. The otherzeolites which may be produced having a coordinated fluoride contentinclude those designated Zeolite L, D, R, S and T. Also many naturallyoccurring zeolites which can also be synthesized can be produced havinga coordinated fluorine content. These include mordenite, chabazite,offretite, ferrionite, clinoptilolite, faujasite, gmelinite and erioniteas well as other.

In essence, therefore, any crystalline zeolite which can be synthesizedfrom component mixtures can be provided with an unwasha-ble, coordinatedfluoride content which enhances the stability of the crystalline zeolitestructure. The mechanism of this st-abilizing eifect of coordinatedfluoride is not presently known, but it is hypothesized that the aluminain the zeolite is prevented from undergoing reorientation.

The various modes of synthesis of the zeolites, and particularly A, Xand Y, are generally known. These may be produced either from thehydrothermal conversion of a clay such as metakaolin or halloysite, orby the reaction of an active silica source solution and an activealumina source solution. Of course, when a particular zeolite is to beproduced, the reactant ratios, one to the other, must be adjusted sothat a particular zeolite can be produced. As exemplary of this point,the reactant ratios for producing a zeolite Y are in the range of 3 andfor zeolite A in the range of Na O/SiO 0.8-1.4 SiO /Al O 1.8-2.2

H O/Na O 30-60 The useful reactant ratios for the other zeolites caneasily be calculated from their known formulae or obtained from theliterature. I

Further, in the formation of these crystalline zeolites, it has beenfound very useful to add a zeolite seed mixture. Such a seed solutionmixture has a composition in the range of 8-30 Na O, 50 SiO 0.1-4.0 A1 050- 500 H O. These seed mixtures have been found to significantlyaccelerate the formation of crystalline zeolites. It is hypothesizedthat this solution forms nuclei which are active centers for zeolitecrystallization.

The fluoride which is to be coordinated into the crystal structure ofthe zeolite must be one which is soluble or at least partially solublein the aqueous active silica and active alumina solutions used tosynthesize the zeolite. Very useful and preferred sources of flourideions are the fluorides and fiuosilicates of monovalent, divalent ortrivalent metals, ammonia, hydrogen or quaternary ammonium cationicelements. The gram amount of fluoride source used depends on severalfactors. These are principally the amount to be coordinated into thezeolite, the degree of solubility of the fluoride source and the amountof fluoride that is available in the fluoride source. By available ismeant the degree that fluoride is present in a dissociated condition.For example, although the fluosilicate ion contains six fluorine atoms,only two can be considered available. That is, only two of the fluorineatoms are present as dissociated fluoride ion and free to be coordinatedinto the zeolite structure.

The total fluorine content which is coordinated into the sieve is in therange of from about 0.01 to 0.15 percent of the total activated zeoliteweight. This fluorine level in the finished zeolite can be accomplishedby use of the following fluoride compound ratios. When the fluoridecontent is to be supplied by a fluosilicate, the ratio of fluosilicateto be used is grams SiF 100 grams A1 0 and preferably grams SiFg 100grams A1 0 grams F 100 grams A1 0 and preferably grams F" 100 grams A1 0to 7 These ratios of fluosilicate and fluoride to alumina content of theactive alumina source solution have proven very effective in producing acoordinated fluorine content of 0.01 to 0.15 percent in the synthesizedcrystalline zeolite.

In the preferred process of the invention, the required amount of anactive silica solution, usually a sodium silicate solution, and therequired amount of an active alumina solution are admixed along with thecalculated amount of fluoride source solution. The fluoride sourcesolution can be added separately or as a comixture with the silicate oractive alumina solution. The active alumina solution may be an aluminatesolution or an aluminum salt solution such as aluminum sulfate, or amixture of these active alumina sources. At this stage, also, a zeoliteseed solution can be added in an amount up to about 10 percent of thetotal weight of the solution. This multicomponent admixture is stirredor otherwise agitated to completely disperse the components. A slurryforms and in the next step this slurry is aged and/or crystallized.Aging consists of maintaining the dispersed admixture at about 20 to 120C. for from about 1 to 48 hours. This aging can be an aging at a singletemperature, or one conducted at two or more temperature ranges. When azeolite seed solution is added, the necessary aging period is decreasedto 1 to 12 hours and is usually conducted at from 70 to 120 C. However,when a zeolite seed solution is not added there is conventionally a coldaging at 20 to 70 C. during which crystallization nuclei form, followedby a hot aging at from 70 to 120 C. during Which crystallization occurs.Such aging techniques are known in the art and have been practiced forsome time. Further, it has been the practice in some instances toagitate the slurry during these aging periods. Crystallization isnormally complete in about 1-24 hours, depend ing on the zeolite beingformed.

Of course, this procedure is capable of variation. A seed mixture neednot be added. Further sources of silica other than sodium silicate canbe used, as can sources of alumina other than aluminum sulfate oraluminate. These, however, are variations known in the art and areessentially equivalent to the above outlined procedure.

After crystallization is completed, the zeolite can be washed, dried andactivated, or it can undergo an ion exchange to remove part orsubstantially all of the sodium ion content. Exchange can be by any ofthe known techniques to produce zeolites having a sodium ion content ofless than 0.1 percent (calculated as Na O). The exchanging ion may bepotassium, ammonium, alkaline earth, rare earth or a transition metalion, or a mixture of substances from this class. The result in anyinstance will be a fluorided zeolite of low sodium content alsocontaining any added ions.

The following examples are set out to further amplify the presentinvention.

Example 1 This example illustrates the formation of fluorided zeolite Yusing ammonium fluosilicate as the fluoride source. This example alsoillustrates the embodiment of the fluoride source being in admixturewith an active source (sodium silicate).

As a first step, the four reactions solutions were separately preparedas follows.

Solution 1 consists of 2058 grams of 37B. sodium silicate is mixedthoroughly with 392 grams of a seed solution having the composition 16Na O:Al O :15 S10 320 H 0 and formed from an admixture of a sodiumsilicate and sodium aluminate solution.

Solution 2 consists of 116 grams of aluminum sulfate dissolved in 313grams of water.

Solution 3 consists of 13 grams of ammonium fiuosilicate dissolved ingrams of water.

Solution 4 consists of a sodium aluminate solution prepared bydissolving 106 grams of hydrated alumina in 152 grams of 50.5 percentsodium hydroxide solution. Dissolution is by heating. 282 grams of wateris then added to this solution.

Solution 3 was added to solution 1 with mixing. Solution 2 is then addedto this combined admixture of solutions 1 and 3 with mixing, followed bythe addition of solution 4 with mixing. A slurry formed and this slurrywas hot aged at 95 C. to C. for 11 hours. The resulting slurry productmix was diluted with water, filtered, washed free of mother liquor anddried. The product has an X-ray crystallinity of 89 percent of astandard sample, a surface area of 996 M /g. fluorine content of 0.032percent (dry basis) and a SiO /Al O ratio of 5.0.

As a basis for comparison, a zeolite sample was also produced using theabove solutions 1, 2 and 4. That is, no fluoride ion was added. The sameprocedure was also used. The product zeolite had an X-ray crystallinityof 91 percent, surface area of 847 M /g. and a Slog/A1203 ratio of 4.7.The fluoride content was nil.

Example 2 This example illustrates the formation of fluorided zeolite Yusing varying ratios of ammonium silicofluoride. This example alsoillustrates the embodiment of the fluoride source being in admixturewith an active alumina source (aluminum sulfate).

As a first step, the four reactions solutions were separately preparedas follows:

Solution 1 consists of 2058 of 37 -B. sodium silicate is mixedthoroughly with 392 grams of a seed solution having the composition 16Na O':Al O SiO :320 H 0 and former from an admixture of a sodiumsilicate and sodium aluminate solution.

Solution 2 consists of 116 grams of aluminum sulfate dissolved in 313grams of water.

Solution 3 consists of either 6.5 grams, 13 grams or 26 grams ammoniumfluosilicate dissolved in 100 grams of water.

Solution 4 consists of a sodium aluminate solution prepared bydissolving 126 grams of hydrated alumina in 182 grams of 50.5 percentsodium hydroxide solution. Dissolution is by heating. 282 grams of wateris then added to this solution.

Solution 3 was added to solution 2 with mixing. Solution 1 is then addedto this combined admixture of solutions 1 and 3 with mixing, followed bythe addition of solution 4 with mixing. A slurry formed and this slurrywas hot aged at 95 C. to 105 C. for 9 hours. The resulting slurryproduct mix was diluted with water, filtered, washed free of motherliquor and dried.

The same addition procedure was conducted for each of the differentammonium fluosilicate contents in solution 3. Table 1 below sets out theproperties of each of the produced zeolites with respect to fluoridecontents.

Example 3 This example illustrates the synthesis of a fluorided zeoliteY using ammonium fluoride in place of ammonium fluosilicate as thefluoriding agent.

As a first step, the four reactions solutions were separately preparedas follows.

Solution 1 consists of 2058 grams of 37 B. sodium silicate is mixedthoroughly with 392 grams of a seed so- =lution having the composition16 Na O:Al O :15 SiO 320 H 0 and formed from an admixture of a sodiumsilicate and sodium aluminate solution.

Solution 2 consists of 197 grams of aluminum sulfate dissolved in 313grams of water.

Solution 3 consists of 6 grams of ammonium fluosilicate dissolved in 100grams of water.

Solution 4 consists of a sodium aluminate solution prepared bydissolving 106 grams of hydrated alumina .in 152 grams of 50.5 percentsodium hydroxide solution.

Dissolution is by heating. 282 grams of water is then added to thissolution.

Solution 3 was added to solution 1 with mixing. Solution 2 is then addedto this combined admixture of solutions 1 and 3 with mixing, followed bythe addition of solution 4 with mixing. A slurry formed and this slurrywas hot aged at 95 C. to 105 C. for 11 hours. The resulting slurryproduct mix was diluted with water, filtered, washed free of motherliquor and dried.

The product zeolite has an unwashable fluorine content of 0.029 percent(D.B.), a surface area of 892 M g. and a Slog/A120 ratio of 4.9.

Example 4 This example illustrates the stability of the zeolitesproduced by coordinating in an unwashable fluoride content. A fluoridedzeolite was prepared according to the procedue of Example 1 and had thefollowing characteristics:

X-ray Crystallinity "94%. Cell Size 24.62 A. Surface Area 826 M*/ g.Fluoride, (dry basis) .0.020%. Mol SiO- lAl O Ratio 24.96.

TABLE 2 Cata- Cata- Tests lyst 1 lyst 2 R8203, dry basis, percent 3. 63. 3 Peak height:

After activation at 1,000 F., mm 64 70 After activation at 1,600 F., mrn62 68 Microactivity:

After steaming at 1,050 F., for 24 hours, percent 90. 4 91. 0Microactivity of a standard Re catalyst aiter steaming at 1,050 F. for24 hours, percent 84. 4 84. 4

The fluoride enhances the ability to withstand severe thermal and steamconditions for longer periods of time. Longer term stability at severeconditions is an important factor since catalysts are Within suchenvironments during regeneration cycles.

What is claimed is:

1. A method of producing fluorine containing zeolite molecular sievescomprising:

(a) providing a reaction mixture of an active alumina solution and anactive silica solution wherein the ratio of alumina to silica in saidsolutions is effective to produce a zeolitic composition;

(b) providing a fluoride ion solution wherein said fluoride ionsolutions whereby a slurry forms; the compound selected from the groupconsisting of ammonium fluoride, ammonium fluosilicate, hydrogenfluoride and fluosilicic acid, said anion radical being present in aratio of from 0.5 to 50 percent of the active alumina content of saidreaction mixture;

(c) admixing said active alumina, active silica and fluoride ionsolutions whereby a slurry forms;

((1) aging said slurry at a temperature of from about 20 C. to C. forfrom 1 to 48 hours, whereby a crystalline zeolite is formed which hasfrom about 0.01 to 0.15 percent fluoride coordinated into thecrystalline structure; and

(e) recovering said crystalline zeolite.

2. A method as in Claim 1 wherein said fluoride anion radical isfluoride, and is present in a ratio of about 1 to 7 percent of theactive alumina content of said reaction mixture.

3. A method as in Claim 2 wherein said aging is conducted for a firstperiod at about 20 to 70 C., and for a second period at about 70 to 120C.

4. A method as in Claim 3 wherein said fluoride containing zeoliteformed is selected from the group consisting of zeolite A, zeolite X andzeolite Y.

5. A method as in Claim 1 wherein said fluoride anion radical isfluosilicate, and is present in a ratio of about 3 to 25 percent of theactive alumina content of said reaction mixture.

6. A method as in Claim 5 wherein said aging is conducted for a firstperiod at about 20 to 70 C., and for a second period at about 70 to 120C.

7. A method as in Claim 6 wherein said fluoride containing zeoliteformed is selected from the group consisting of zeolite A, zeolite X andzeolite Y.

8. A method as in Claim 1 wherein a zeolite seed mixture having acomposition of 8-30 Na O 0.1-4 A1 5-50 SiO 50-500 H O is admixed in step(c) with said active alumina, active silica and fluoride ion solutions.

9. A method as in Claim 8 wherein said zeolite seed mixture is added ina concentration of from about 1 to percent by weight of the combinedactive alumina and active silica solution.

10. A method as in Claim 9 wherein said fluoride anion radical isfluoride, and is present in a ratio of about 1 to 7 percent of theactive alumina content of said reaction mixture.

11. A method as in Claim 10 wherein said fluoride containing zeoliteformed is selected from the group consisting of zeolite A, zeolite X andzeolite Y.

12. A method as in Claim 9 wherein said fluoride anion radical isfluosilicate, and is present in a ratio of about 3 to percent of theactive alumina content of said active reaction mixture.

13. A method as in Claim 12 wherein said fluoride containing zeoliteformed is selected from the group consisting of zeolite A, zeolite X andzeolite Y.

14. The product of the process of Claim 1.

15. The product of the process of Claim 8.

References Cited CARL F. DEES, Primary Examiner US. Cl. X.R. 252441, 455Z a UNITED STATES PAT NT OFFiCE CERTIFICATE OF CQRECTIUN Dated October1, 1974 Patent No. 3,839,539

Inventofl Curtis H. Elliott. Jr.

It is eertified that error appears in the above-identified patent andthat said Letters Patent are hereby oorrected as shown below:

Claim 1, part (b) line 47, after- "ion" delete "solutions whereby, aslurry forms" and add is provided by an anion radical from Signed andsealed this 28th day of January 1975.

(SEAL) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM po-1oso (o-69') USCOMM-DC 60376-P69 1 U 5 GOVERNMENTPRINTING OFFICE I BG S 0-366-334

1. A METHOD OF PRODUCING FLUORINE CONTAINING ZEOLITE MOLECULAR SIEVESCOMPRISING: (A) PROVIDING A REACTION MIXTURE OF AN ACTIVE ALUMINASOLUTION AND AN ACTIVE SILICA SOLUTION WHEREIN THE RATIO OF ALUMINA TOSILICA IN SAID SOLUTIONS IS EFFECTIVE TO PRODUCE A ZEOLITICCOMPOSITIONS; (B) PROVIDING A FLUORIDE ION SOLUTION WHEREIN SAIDFLUORIDE ION SOLUTION WHEREBY A SLURRY FORMS; THE COMPOUND SELECTED FROMTHE GROUP CONSISTING OF AMMONIUM FLUORIDE, AMMONIUM FLUOSILICATE,HYDROGEN FLUORIDE AND FLUOSILICIC ACID, SAID ANION RADICAL BEING PRESENTIN A RATIO OF FROM 0.5 TO 50 PERCENT OF THE ACTIVE ALUMINA CONTENT OFSAID REACTION MIXTURE; (C) ADMIXING SAID ACTIVE ALUMINA, ACTIVE SILICAAND FLUORIDE ION SOLUTIONS WHEREBY A SLURRY FORMS; (D) AGING SAID SLURRYAT A TEMPERATURE OF FROM ABOUT 20*C. TO 120*C. FOR FROM 1 TO 48 HOURS,WHEREBY A CRYSTALLINE ZEOLITE IS FORMED WHICH HAS FROM ABOUT 0.01 TO0.15 PERCENT FLUORIDE COORDINATED INTO THE CRYSTALLINE STRUCTURE; AND(E) RECOVERING SAID CRYSTALLINE ZEOLITE.